1. Field of the Invention
The present invention relates, in general, to a controller for refrigeration. More particularly, the invention relates to a compressor controller.
2. Description of the Prior Art
A compressor of a refrigerator is operated in accordance with the temperature in a compartment thereof. The temperature in the compartment is detected by a temperature sensor which is provided in the compartment. When the temperature in the compartment is above a set temperature, the compressor is driven to cool the compartment, while the compressor is halted when the temperature in the compartment is below the set temperature. As a result, the inside of the compartment is kept within the set temperature range. An example of such a compressor control system is disclosed in Japanese Utility-Model Publication No. 58-13275, first laid open on July 8, 1978. In Japanese Utility-Model Publication No. 58-13275, two temperature sensors are provided in a refrigerator. One of the temperature sensors detects the temperature of an evaporator, causing the compressor to turn ON when the temperature exceeds a predetermined value. The other of the temperature sensors detects the temperature in a compartment where the evaporator is placed, causing the compressor to turn OFF when the temperature in the compartment drops below a set temperature.
There are some countries where the power supply voltage value fluctuates rapidly and to a great extent. With a conventional compressor control system, the compressor may fail to start when the refrigerator is used in such a country as described above, because of fluctuations of the power supply voltage. Generally, an overload relay made of a bimetallic strip cuts the power to the compressor. However, because of the bimetallic strip, the compressor may again fail to start after the overload relay reverses to a state supplying power to the compressor. Furthermore, if the overload relay fails or is slow in responding, the compressor motor may burn out, or a power supply circuit breaker may cut the power, causing a power outage.